The present invention relates to a method for controlling an engine braking device for a combustion engine in motor vehicles, in particular in commercial vehicles, to an engine braking device and to a vehicle having the engine braking device.
In air-compressing (diesel) combustion engines in commercial vehicles, there is a known practice of producing an exhaust gas backpressure in the exhaust system using a brake flap in the overrun mode, the backpressure bringing about effective engine braking since the pistons of the combustion engine operate against this exhaust gas pressure during the exhaust stroke (outlet valves open).
In order significantly to increase the effect of such an engine braking device, there is a practice, known from U.S. Pat. No. 5,150,678 for example, of additionally providing a decompression brake, where, in addition to regular valve actuation in accordance with the four-stroke principle, the outlet valves are also partially open during the compression stroke. Here, the additional braking effect arises from the throttled discharge of the combustion air into the exhaust system.
The decompression brake can be either exhaust-controlled or positively controlled. In exhaust-controlled operation, the valve timing of the outlet valves is configured in such a way that the outlet valves open irregularly in a specifically intended manner owing to the exhaust gas backpressure present when the brake flap is closed (“valve jumping”) and are held open by a mechanism until the next regular valve opening.
In the case of a positively controlled decompression brake, interventions are generally made into the regular valve timing by hydraulic and mechanical means in order to hold the outlet valves partially open in a specifically intended manner, at least also during the compression stroke.